Pressure indicator and switch

ABSTRACT

A pressure indicator and light sensitive electric switch device comprising a controlling magnetic helix device carrying a pressure indicating arm, the position of which is controlled by a magnet mounted on the free end of a cantilevered spring actuated by pressure diaphragm. Operably associated with the helix and its indicating arm are a pair of set point arms each having movable herewith a photosensitive device which cooperate a source of light and a light interrupting shield mounted to move with the helix, such that when each photosensitive device is incorporated in a controlling relay circuit, the respective set point arms cooperate with the pressure indicating arm to effect electrical switch operation at preselected high and low pressures.

United States Patent 1191 Phillips et al.

1451 Jan. 21, 1975 1 PRESSURE INDICATOR AND SWITCH [75] Inventors: James W. Phillips, Michigan City; Richard S. Zoludow, South Bend, both of Ind.

[73] Assignee: Dwyer Instruments, Inc., Michigan City, Ind.

[22] Filed: Mar. 22, 1974 [21] Appl. No.1 453,887

250/210; 73/407 R, 407 PR; 324/157 Primary ExaminerWalter Stolwein Attorney, Agent, or Firm-Mann, Brown, McWilliams & Bradway [57] ABSTRACT A pressure indicator and light sensitive electric switch device comprising a controlling magnetic helix device carrying a pressure indicating arm, the position of which is controlled by a magnet mounted on the free end of a cantilevered spring actuated by pressure diaphragm. Operably associated with the helix and its indicating arm are a pair of set point arms each having movable herewith a photosensitive device which cooperate a source of light and a light interrupting shield mounted to move with the helix, such that when each 1561 5ZPli i1$iilifffifni2352212211115 UNITED STATES PATENTS with the pressure indicating arm to effect electrical 3,397,319 8/1968 Locke 250/231 P switch operation at preselected high and low pres- 3,588,516 6/1971 Friedman 324 157 sures. 3,645,140 2/1972 Phillips et a1, 73/407 R 13 Claims, 19 Drawing Figures 2,\ A 96 M M02 144g 4 54 y 20 420 see W 30 14 1 7e 4 14 2 44 36 Moss Patented Jan. 21, 1975 6 Sheet-Sheet 1 mmw Patented Jan.21,11975 I 3,862,416

I 6 Sheets-Sheet Q 2 500 7a I I I Patented Jan. 21, 1975 3,862,416

6 sheets-S eet Patented Jan. 21, 1975 6 Sheets-Sheet 5 Patented. Jan. 21, 1975 r 3,862,416

6 Sheets-=Sheet 6 FIGJQ PRESSURE INDICATOR AND SWITCH This invention relates to a differential pressure indicator and switch, and more particularly, to a combination pressure indicating gauge and switch which acts both as a pressure indicator and a pressure control switch.

Locke US. Pat. No. 3,397,319 discloses a differential pressure indicator and switch in which the pressure indicating element is actuated by a magnetic helix device that is in turn controlled by the differential between pressures on either side of a diaphragm. The device is made a pressure control switch by employing a source of light, a light sensitive element movable with a set point arm, and a light interrupting shield in which the shield is mounted for movement with the helix to interrupt or allow passage of light to the light sensitive element at predetermined pressure differentials as determined by the position of the set point arm. By connecting the photosensitive device into a relay circuit, an electrically actuated switch can be made to open and close at a preselected pressure and thereby control absolute or differential fluid pressure.

In this type device, the helix is journaled on a wish bone mounted cantilever style and cooperates with a permanent magnet mounted on a leaf spring that is connected to a diaphragm for movement thereby under the movement of the diaphram resulting from differences in pressure on either side of the diaphragm.

A principal object of the present invention is to generally improve devices of this type for facilitating manufacture, assembly and installation of same, and to generally improve their performance.

Another principal object of the invention is to improve the arrangement of the wishbone and manner of mounting the pressure indicating and switch controlling components on same, as well as to adapt the hand knob controls for the set point arms to accommodate zero setting of the wishbone.

Another important object of the invention is to provide an improved prong plug arrangement in the housing back wall for connecting the instruments internal wiring to the external wiring involved, and to provide a relay pack arrangement that may be alternately connected directly to the gauge housing back plate or mounted remotely from the instrument.

Other objects of the invention are to provide a combination pressure gauge and switch device that is economical to manufacture, convenient to install and use, and long lived in operation.

In accordance with the invention, the wishbone of the device is shaped to define a planar mounting panel portion that faces outwardly of the instrument housing open end, on which are journaled the set point arms and controlling gearing therefor, which are disposed on the upwardly facing side of the wishbone, and thus are positioned for ease of inspection and repair. Each set point arm employed has a photocell mounted for movement with same that is positioned for exposure to a source of light located at the axis of rotation of the helix, with the helix mounting the light interrupting shield that is located intermediate the helix axis and the respective photosensitive devices, and that is shaped to be concentric with the helix axis for accurate cooperation with the respective photosensitive devices.

The internal wiring for the light source and photocells extends to a special back wall pronged plug that is potted in place in a manner to effect a good fluid tight seal about the prongs and also seal the pores of the metal about the opening in which the plug is disposed.

Adapted to be assembled with the back wall of the gauge housing is a relay pack which includes the relay pack which includes the relay coils that are controlled by the application of light to, or the shielding of light from, the photocells involved for each set point arm. The relay pack is mounted on the bracket structure that can be affixed to the housing back wall or mounted remotely from same.

The relay pack includes a special semi-conductor control arrangement incorporating the relay coils and photocells in a control circuit whereby a pair of switching semi-conductor devices are operably associated with each relay coil that are reversed as to bias, for purpose of energizing, or deenergizing the relay coil served by each pair, by rendering the photocell involved for each pair of semi-conductors conductive or nonconductive, through the use of the light interrupting shield and the positioning of the set point arms relative to the gauge scale.

Other objects, uses, and advantages will be obvious or become apparent from a consideration of the following detailed description and the application drawing in which like reference numerals indicate like parts throughout the several views.

In the drawings:

FIG. 1 is a diagrammatic perspective view illustrating one embodiment of the invention;

FIG. 2 is a side elevational view of the device as it may be mounted in operating position, with the relay pack cover shown displaced from its normal mounting position;

FIG. 3 is a plan view of the front or face of the instrument, with the instrument front cover omitted and the instrument dial indicated in dashed lines only;

FIG. 4 is a fragmental cross-sectional view taken substantially along line 4-4 of FIG. 3;

FIG. 5 is a fragmental view taken substantially along line 5-5 of FIG. 3;

FIG. 6 is a fragmental view taken substantially along line 6--6 of FIG. 3;

FIG. 7 is a plan view of a locking ring used in connection with the prong plug shown in FIG. 4;

FIG. 8 is an elevational view of the locking ring shown in FIG. 7, taken substantially along line 8-8 of FIG. 7, with the prong plug shown applied thereto;

FIG. 9 is a front plan view of the wishbone assembly shown in FIG. 3, with the light support shown in FIG. 5 omitted;

FIG. 10 is a side elevational view of the structure shown in FIG. 9, with the light support shown in its mounted position;

FIG. 11 is a diagrammatic cross-sectional view FIG. is a sectional view taken substantially along line 15l5 of FIG. 14;

FIG. 16 is a fragmental sectional view taken substantially along line 1616 of FIG. 15;

FIG. 17 is a diagrammatic illustration of the electric circuit forming a part of the device arranged to operate two switches;

FIG. 18 is a view similar to that of FIG. 11 but illustrating a modified form of the invention; and

FIG. 19 is a view similar to that of FIG. 17 illustrating an electrical circuit adapted to operate a single switch.

However, it is to be distinctly understood that the specific drawing illustrations provided are supplied primarily to comply with the requirements of the Patent Laws, and that the invention is adapted to have other embodiments which will be obvious to those skilled in the art, and which are intended to be covered by the appended claims.

GENERAL DESCRIPTION Reference numeral 10 of FIGS. 1 and 2 generally indicates one embodiment of the invention which comprises pressure gauge 11 including a housing 12, formed from a suitable nonmagnetic material, such as aluminum, suitable aluminum alloy, or a suitable plastic, having an open end 14 (FIG. 14) closed by a cover 16 of transpartent plastic material held in place by annular cap or bezel l8 threadedly secured to the housing 12 as indicated at 20 (see FIG. 11).

The housing 12 includes rear wall 22 (see FIG. 11) defining a saucer shaped portion 24 which, in the form of FIGS. 1-17, forms a stationary wall for low pressure chamber 26. The chamber 26 is closed by flexible diaphragm 28 formed from a silicone rubber or the like, supported on either side of the same by metallic plates 30 and 32. Diaphragm 28 is suitably mounted in place at its rim and fastened between plates 30 and 32 at the center of the diaphragm to connecting link 34 comprising a rod element 36 having its ends 38 and 40 threaded, to which nuts 42 are applied to either side of the plates 30 and 32 on the end 40 to clamp the diaphragm in leakage-free relation therebetween (boss 25 serving as a stop for link 34). Nuts 44 applied to the end 38 of the rod member 36 and disposed on either side of the leaf spring 46 connect the rod element 38, and thus the diaphragm 28, to the leaf spring 46. Leaf spring 46 is cantilever mounted at its end 48 by employing suitable screws 50, which are applied to the housing wall 22 in such a manner as to clamp the end 48 of spring 46 against a slide structure 52 which mounts a U-shaped clamp 54 for adjusting the live length of the spring 46, as per the arrangement shown in said US. Pat. No. 3,397,319.

On the free end 56 of the spring 46 is mounted a horse shoe shaped magnet 58 (of the type disclosed in said patent) cooperating with helix 60 that is journaled at the free end 61 of a wishbone 62 with the other end 64 of the wishbone being secured cantilever fashion to the housing 12 by suitable screws 66.

The helix 60 carries differential pressure indicating arm 68 which cooperates with suitable scale indicia 71 suitably applied to scale plate 72 which is secured to the wishbone 62.

In accordance with this invention, the wishbone 62 adjacent its end 64 defines a planar scale plate mounting portion 74 to which the scale plate 72 is secured by suitable screws applied to screw holes 76 formed in the wishbone. The wishbone is also formed to define a mounting panel portion 78 that is off set above the level of the scale plate mounting portion 74 to define a window opening 80 (see FIG. 11) through which the indicator arm 68 extends.

Mounted on the mounting panel portion 78 of the wishbone 62 are a pair of gear segments 82 and 84 that respectively have secured thereto the respective set point arms 86 and 88 which also cooperate with the scale indicia 71 of the scale plate 72 to provide. in accordance with this invention, switch control at selected high and low pressures.

The gear segments 82 and 84 are mounted on the panel portion 78 for pivotal movement about the axis 70 of the helix 60. The gear segment 82 is pivoted by turning knob 90 (see FIGS. 1 and 2) that is journaled in cover 16 and that has a splined connection 92 with a handle element 94 connected by a suitable friction clutch arrangement 96 to gear 98 suitably journaled on the wishbone mounting portion and meshing with idler gear 100 (see FIG. 3) similarly journaled on the wishbone mounting portion and meshing with the teeth 102 of the gear segment 82.

Similarly, the gear segment 84 is pivoted for movement about the axis 70 utilizing knob 104 connected to a second handle element 106 which is in turn keyed to gear 108 through a suitable friction clutch arrangement that is the same as arrangement 96, which gear 108 meshes with idler gear 110 also journaled on the wishbone panel portion for meshing engagement with the teeth 111 of the gear segment 84. Thus, the gear segments 82 and 84 may be pivoted in the same direction as the knobs 90 and 104 are turned to set the respective set point arms.

The gear segment 82 has adjustably mounted on same photocell 112 of any suitable type having a light receiving face 114 provided (see FIG. 6) with a light blocking coating 116 that is scratched or slit to define a narrow rectilinear light receiving opening 118, having a width on the order of 0.007 inch, across the structure 1 14 that is adapted to receive light from a suitable long life light bulb 120 that is mounted in alignment with the axis 70 of the helix 60. The face 114 of the photocell 112 is adapted to be shielded from the light bulb 120 by light interrupting shield 122 which is fixed to and moves with indicator arm 68, as indicated in FIGS. 3, 5, 9, and 11 13, is disposed above the wishbone mounting panel portion 78 in concentric relation to the helix axis 70.

Gear segment 84 has adjustably mounted on same a similar photocell 113 which is identical to the photocell 112. The light shield 122 includes an upstanding arcuate wall that is concentric with the helix axis 70, and has an edge 132 which shuts off the light to photocell 112, and an edge 134 which shuts off the light to photocell 113, when the helix, and thus indicator arm 68, has the proper relation with set point arms 86 and 88, respectively, which thus set the high and low pressure functioning points of the respective photocells 112 and 113.

The wishbone 62 is formed to define a shoulder (see FIG. 11) that is engaged by a nut member 142 threadedly mounted on zero adjust screw 144 which is suitably journaled in the housing and of the general type shown in said US. Pat. No. 3,397,319, actuated by a headed stud member 146 that is slidably mounted in cover 16 and includes a hex end portion 148 for reception in the socket 150 of the zero screw 144. The stud 146 is mounted in leak proof relation with cover 16, with the splined connections 92 and the mounting of the stud member 146 in the cover permitting the zero adjust movement of the free end 61 of the wishbone that is contemplated by the nature of the zero adjust device employed.

The photocells 112 and 113 are incorporated with light 120 in the electrical circuit diagrammatically illustrated in FIG. 17 to control, for instance, switches 160 and 162 (see FIG. 17) that may be employed to provide the high pressure and low pressure controls possible utilizing the device 10, with the switches 160 and 162 being operatively associated with the relays 164 and 166, respectively, that respectively include the respective relay coils 165 and 167. Relays 164 and 166, in accordance with the invention, form a part of the relay pack 168 which, in accordance with this invention, may be affixed to the housing back wall 22, with the wiring for the photocells 112 and 113 and bulb 120 extending from these components to a pronged plug 170 (see FIG. 4) mounted by potting in opening 172 formedin the housing back wall 22. Back wall is bossed as at 174 in alignment with the opening 172 to define a potting recess 176 for potting in place (using a suitable epoxy), the pronged plug 170 for also providing leakage free sealing relation with respect to the individual prongs 178 as well as the grain of the metal defining the opening 176 and about plug 170. The prongs 178 are sufficient in number to serve as a connection for each wire involved in connection with the photocells 112 and 1 1-3 and light bulb 120 to make the electrical connections indicated in the circuit of FIG. 17 from the outside of the plug 170 as indicated in FIGS. 4 and 14.

The relay pack 168 generally comprises a generally U-shaped mounting bracket 180 (see FIG. 14) defining spaced apart arms 182 and 184 extending from the web portion 186 that is fixed to the back wall 22 of the housing 12 by suitable nuts 188 and 191 (see FIG. 11), respectively applied to threaded stud members 192 and 194 that are suitably mounted in the housing back wall 22. In the form shown, a separate back plate 195 that overlies the entire back side of the housing 12 is interposed between the.bracket web 186 and the back side of the housing to insure a firm securement of the bracket 180 by the two screw and nut mountings that have been indicated.

Interposed between the bracket arms 182 and 184, and secured thereto by screws 187 and 189 is an electrical connection panel 190 having circuit boards 192 and 194 secured thereto for application of the electrical components indicated by the wiring diagram of FIG. 17, and having applied to the other side of the mounting panel 190 suitable connecting screws 196 for application thereto of the connecting wires that are to be connected to the various pieces of apparatus to be controlled by the switches 160 and 162, through a suitable pronged electrical plug structure 198 suitably mounted in the projecting end portion 200 of the bracket arm 184.

In the wiring diagrams of FIGS. 17 and 19, transformer 210 has its primary suitably connected to a source 212 of electrical power and its secondary connected to a packaged bridge rectifier assembly 214 for supplying DC current to the control circuit in which the photocells 112 and 113 employed are connected.

Operatively associated in the circuits of FIGS. 17 and 19 with the photocell 112 are a pair of NPN switching transistors 216 and 218, with the circuit being arranged so that when the high set point photocell 112 is shielded from the source of light represented by bulb 120, relay coil 165 is energized (to close switch through transistor 216 by reason of the transistor 216 being biased to its conductive state, but on exposure of the photocell 112 to the light source, as would be occasioned by movement of the light shield 122 sufficiently counterclockwise of FIGS. 3 and 9, the photocell 112 becomes conductive, resulting in a switching of the transistor 218 from a non-conductive to a conductive state, which in turn has the effect of switching the transistor 216 to its non-conductive state and deenergizing the coil to open switch 160.

As to the low set point photocell 113, it is operatively associated with a pair of NPN switching transistors 220 and 222 arranged so that when the photocell 113 is exposed to the light source, transistor 222 is biased to its non-conducting state which results in the transistor 220 being biased to its conducting state and the relay coil 166 being energized through the transistor 220 to maintain the switch 162 closed. Shielding of the photocell 113 from the source of light renders transistor 222 conductive which has the result of rendering transistor 220 non-conductive and deenergization of coil 166.

In the device 10A of FIG. 18 the relay pack (not shown) is remotely located, and the back wall 22A of housing 12A in the area of its saucer shaped portion 24, and at the boss 25, is formed with an opening 230, and the back side of the back wall 22A is recessed, as at 232, for formation of a special diaphragm chamber 234 by cap 236 secured in place by suitable screws 238 and clamping a diaphragn 240 in fluid tight sealed relation about the margin of the cap 236.

The diaphragm 240 has diaphragm plates 242 and 244 received on either side of same that are clamped against the diaphragm 240 by suitable nut 246 applied to the threaded end 247 of rod member 248 against hub 249 fixed thereto, member 248 has its other end 250 suitably threaded for connecting same to leaf spring 46 by application thereto of suitable nut 252 against hub 254 that is suitably fixed to the rod member 248.

In the device 10A, the section 256 of chamber 234 that is formed by the diaphragm 240 is the high pressure chamber of the device, the cap 236 being formed with threaded opening 260 adapted for connection to a source of fluid under high pressure, it being understood that the space within the housing 12A on the other side of diaphragm 240 is the low pressure side of the device in the arrangement of FIG. 18. Helix 60A is of reverse turn or hand, with the remainder of the parts of the device 10A being the same as described above.

The device 10A is particularly adapted for use in connection with artificial kidney machines for blood purification. Diaphragm 240 is located for ready exposure and cleaning, by removing the cap 236, in the event that chamber section 234 becomes contaminated with blood. Diaphragm 240 is formed from a material compatible with fluids conventionally used to clean equipment exposed to blood, Du Ponts Viton fluoruelastomer product, reinforced with Dacron fabric being employed in one operating embodiment.

The circuit of FIG. 19 is similar to that of FIG. 17, but is a single circuit, utilizing photocell 112 and the relay coil it controls.

SPECIFIC DESCRIPTION The housing 12 and its associated parts are adapted to be mounted in the manner indicated in FIG. 2 by forming in a suitable supporting panel 300 an opening proportioned to closely receive the side wall 302 of the bezel 18. Mounted on the bezel 302 is a mounting ring 304 carrying a plurality of screws 306 that are adapted to be threaded against the panel 300 so as to clamp the panel between the screws 306 and the shoulder 308 of the bezel, with the mounting ring 304 bearing against lock ring 308 that is carried by the bezel side wall 302 (see FIG. 11).

In the form of FIG. 2, the relay pack 168 is connected to the housing 12 and a suitable flexible conduit 310 is connected to the pronged plug structure 190 in any suitable manner for incorporating the circuiting of the relay pack 168 in the overall control circuiting that is desired.

The relay pack 168 is covered by housing or cover 312 that is preferrably formed from a suitable transparent plastic material and is proportioned to entirely cover the relay pack 168 except for a side wall 314 which is formed to define a slot 316 that is grooved on either side of same, as at 318 to frictionally receive the sides 317 and 319 of the bracket leg 184. The cover or housing 312 is flanged as at 320 for application thereof of suitable screws to secure same to the bracket mounting plate 188, with a suitable layer of cork 322 (see FIG. 14) being applied substantially about the outwardly facing margin of the plate 195 to provide for uniform clamping engagement of the cover flange 320 to the mounting plate 195.

The general arrangement of the housing 12 and the mounting of its diaphragm 28 may be substantially as disclosed in said US. Pat. No. 3,397,319. The dia phragm 28 thus has a beaded marginal edge 330 received in groove 332 formed in the housing about saucer portion 24 and held in place by the saucer shaped plate 334 being secured in place against the diaphragm beaded edge by suitable lock ring 336 applied to circular recess 338 formed in the housing.

The wishbone 62 is of one piece construction shaped to define spaced apart legs 350 (to which screws 66 are applied to cantilever mount the wishbone) as well as the planar scale plate mounting portion 74 and the planar mounting portion 78 on which the set point adjustment gearing are journaled. It will be noted that the wishbone mounting portion 78 provides a one piece mounting member arrangement for the set point gearing that is involved which facilitates accurate journaling of the various parts involved on the wishbone.

The wishbone at its free end 61 defines a flange portion 352 that is disposed normally of the wishbone portions 62 and 78, and is provided with a ledge portion 354 (see FIGS. and 11) that is disposed generally parallel to the wishbone portion 62 and 78 for journaling application of the helix to the wishbone 62, with the ends of the helix being suitably mounted in jeweled bearings (not shown) suitably secured to the wishbone portions 78 and 354.

The wishbone at its free end 61 is formed with a window opening 356 (see FIG. 11) into which extends the arm 358 that is fixed to the helix 60 for purpose of mounting both the indicator arm 68 and the light shield 122. Arm 358 has a riser portion 360 on top of which is applied the light shield 122, with the riser portion 360 disposing the light shield 122 just above, but in closely spaced relation to the gear segments 82 and 84, in concentric relation with the axis 70 of the helix.

The light shield 122 comprises a generally planar annular portion 362 formed with a polygonal opening 364 adapted to receive a similarly shaped boss portion 366 of the riser 360, with suitable screw 368 securing the light shield in place on the arm 358. The light shield 122 is flanged about a predetermined portion of its marginal edge to define the light shield portion 130 for cooperation with the photocells 112 and 113.

The photocells 112 and 113 may be of any suitable construction that are triggered by light to conduct electricity in which becomes substantially non-electrically conductive when in the darkened state, such as the silicon PNPN photocell made and sold by Solid State Products, Inc. of Salem, Mass. under the trademark MICRO PHOTRAN. In the form shown, each photo' cell includes a housing 370 (see FIG. 6) provided with laterally extending mounting lugs 372 each of which is slotted as at 374 to receive suitable mounting screws 376. The elongate nature of the openings 374 permits adjustment of the individual photocells for setting their location as desired relative to the light shield 122 and light bulb 120.

In the form shown, the mounting panel portion 78 of the wishbone is formed with a semicircular recess 380, by indenting the metal from which the wishbone is formed inwardly of the housing, to define an arcuate pathway accommodating the shanks of the screws 376 which project through the respective gear segments.

The light 120 is mounted in position by being suitably secured to the T-shaped mounting member 382 that is suitably affixed to the U-shaped mounting member 384 that is secured to the free end 61 of the wishbone, over the window opening 356, by application of suitable screws 386 thereto. For convenience, the wiring leading to the light 120 and the respective photocells may also be suitably mounted on the bracket 384, substantially as indicated at 388 in FIG. 3.

As indicated in FIG. 11, the splined connections 92 between the respective knobs and 104 involve the respective handle members 94 and 106 which are each formed with a flattened splined portion 390 that is slidably received in similarly proportioned slot 392 formed in the respective knobs 90 and 104. The friction clutches 96 may be of any suitable type, that shown comprising suitable compression spring 394 applied between the gear (98 or 108) that is to be controlled by the spindle 94 or 106 and a washer 396 abutting against a flange 398 of the respective spindles.

In the form shown, the respective handle members 94 and 106 extend through the wishbone mounting portion for securement in place by having a washer 400 (see FIG. 10) received behind an enlarged end 402 of same to journal the respective handle members on the wishbone (see FIG. 10).

The gears and 110 are journaled in their operating positions by being rotably received over bossed portions 410 of the respective disc members 412 that are secured in place by the respective screws 414 (see FIGS. 3 and 9).

The bezel 18 is applied to the cover 16 by the threaded connection indicated at 20, preferrably against suitable O-ring seal 420 (see FIG. 11) interposed between the two for fluid sealing purposes. The respective knobs 90 and 104 are permanently mounted in the cover 16 by employing suitable lock rings 422, and are preferrably operably engaged with suitable fluid tight O ring seals 424 (see FIG. 11). The head 430 of zero adjust spindle 146 preferrably is suitably equipped with O-ring seal 432 (see FIG. 11) that is fluid tight sealing relation with a cover 16, as well as a sleeve 434 that has a bore of less diameter than the width of the shank hex portion 148 to preclude withdrawal of the spindle 146 from the cover 16.

The general arrangement of the zero adjust screw 144, in terms of its mounting and application to the wishbone, may be substantially in accordance with said US. Pat. No. 3,3973 19. However, it is to be noted that the splined connections 92 for the knobs 90 and 104 and the shiftable mounting of the zero adjust panel 146 accommodate movement of the free end 61 of the wishbone that is effected by the operation of the adjust screw 144 without disturbing the fluid tight seals at the cover 16 in the area of the knobs 90 and 104 and the zero adjust spindle 146.

The pronged plug 170 comprises shank 440 that is threaded for application to threaded opening 172 of the housing back wall 22. The prongs 178 are suitably mounted in the plug 170 in some convenient manner to insure that they will be electrically insulated from one another. The plug 170 in the form shown includes a hex shaped head portion 442 that cooperates with locking clip 444 which anchors the plug 170 against threading movement with regard to the housing. The locking clip 444 comprises an annular member 446 (see FIG. 7) formed with a depending flange 448 adapted to seat in a recess 450 formed in the housing back wall for this purpose, as well as a pair of opposed side walls 452 and 454 adapted to grip or engage operatively disposed hex faces 456 of the plug head 442 (see FIG. 8). With the flange 448 seated in recess 450 and the flanges 452 and 454 engaging opposed hex surfaces 456 of the plug, the plug will be securely held against dislodgement.

The flanges 452 and 454 are formed with the respective holding wings 457 and 458 which serve as retainers for the plug of an extension cord employed when the relay pack 168 is'to be vertically mounted. Wings 457 and 458 are provided with oppositely disposed tabs 459 and 461 that serve as stops to limit rotation of such plug such that the plug would disengage from clip 444.

Referring now more particularly to the relay pack 168, the manner of application of the components of electrical circuits of FIGS. 17 and 19 to the circuit boards 192 and 194 is largely optional, though in the case of the transformer 210 the transformer housing 460 about the margin of its base 462 is formed with six clinching fingers 464 that extend through suitable openings 466 formed in the circuit board for firm clenching engagement with the circuit board 194, in the manner indicated in FIG. 16.

The circuit board 194 is secured to the mounting panel 190 by three screws 467 that provide a sturdy three point mounting for the circuit board 194. It is also preferrable to use braided leads to the transformer 210 instead of solid wire leads as the braided lead type better withstands shock.

Referring now more particularly to electrical circuit of FIG. 17, the transformer 210, the rectifier assembly 214, the capacitators indicated at 470, 472 and 474,

and diode 476, provide a dual polarity power supply for the double circuit arrangement of FIG. 17.

The double circuit of FIG. 17 in association with the high set point photocell 112 involves voltage dividing resistors 478, 480 and 482, capacitor 484, and resistor 486.

The transistor 216 has its collector 490 and its emitter 492 in series with the relay coil 165, and its base 494 connected to the collector 496 of transistor 218, the latter transistor having its emitter 498 connected to the common lead 479.

The diode 476 acts as an isolation diode which has the effect of keeping operation of the relays from adversely affecting the electronic circuitry that is involved in association with the photocells.

The photocell 113 has operatively associated with same. voltage dividing resistors 500 and 502, capacitor 504, and resistor 506. The collector 508 of the transistor 220 and its emitter 510 are in series with relay coil 167, with the base 512 of transistor 220 being connected to the collector 514 of transistor 222 which had its emitter 516 connected to the common lead 479. The base 479 of transistor 218 and the base 518 of the transistor 222 are respectively connected with the respective photocell circuits for biasing the transistors 218 and 220 between their conducting and non-conducting conditions respectively. With regard to the photocell 112 and the relay coil 165 it controls, when the photocell 112 is shielded from the light by the light shield 122, photocell 112 is substantially electrically nonconductive, whereby a negative voltage is present at the base 497 of the transistor 218 via voltage dividing resistors 478, 480 and 482 which act as base biasing resistors. The capacitor 484 charges to a negative potential with respect to the collector voltage of transistor 218. The collector voltage of transistor 218 becomes high because the transistor 218 is biased to a nonconducting state and the voltage involved also appears at the base of transistor 216 causing the transistor 216 to assume a heavily conductive state from collector to emitter which causes the collector pins involved to assume a negative voltage with respect to the positive voltage at capacitor 484 whereby relay coil 164 is energized.

When the photocell 112 becomes exposed to the source of light by repositioning of the light shield, the photocell 112 then becomes electrically conductive, which produces a positive voltage at the base 497 of transistor 218 via the voltage dividing resistors 478, 480 and 482, which biases the transistor 218 to its conducting state. The impedance between the collector and emitter of the transistor 218 now is low causing a voltage drop across resistor 486 which reduces the potential at the base 494 of transistor 216 which forces the impedence between the collector and emitter of the transistor 216 to become high and thus render transister 216 substantially non-conductive, therefor deenergizing the relay coil 164.

As to the photocell 113, when the photocell 113 is in the dark state, transistor 222 is biased in a positive mode via resistor 502 which causes the collector to emitter impedence of transistor 222 to become low thereby causing a voltage drop across resistor 506. This thus makes the voltage at the base of transistor 220 low and thus the impedence between the collector and emitter of the transistor 220 high, thereby effecting deenergization of coil 166.

When the photocell 113 is exposed to light by appropriate positioning of the light shield, the photocell 113 become electrically conductive and via resistor 500 provides a negative voltage at the base 518 of transistor 222, which causes the collector to emitter impedence of this transistor to assume a high value and thus reduces the voltage drop across resistor 506. This provides a positive voltage at the base 512 of transistor 220 which had the effect of making low the collector to emitter impedence of the transistor 220 and effects en ergization of relay coil 166.

The capacitors 484 and 504 act as a damping device to prevent the transistors 218 and 222 from operating momentarily when voltage is introduced to the circuit. This particular feature reduces the chance of an error operation when the power is turned on to the circuit of FIG. 17.

Obviously, relays 164 and 166 may be employed to close normally open switches or open normally closed switches, depending on the electrical circuiting desired.

The circuit of FIG. 19 operates in substantially the same manner as described with regard to the photocell 112 in view of the fact that the circuit of FIG. 19 is a single circuit for the photocell 112.

In accordance with one embodiment of the invention, the electronic circuiting involved is arranged so that for a 117 volt alternating current 50-60 cycle power source, the dual polarity direct current power supply will be a positive volt direct current and a negative 10 volt direct current with respect to the common line 479.

Several advantages to the electronic switching arrangement indicated are as follows:

1. There is high noise and interference immunity to accidental energization of the relay coils.

2. The arrangement of the capacitors 484 and 504 in a Miller integrator configuration reduces start up errors.

3. The high level switching by the non-critical voltage biasing arrangement illustrated insures positive switching action regardless of line voltage change.

While relay driver circuits as such are known, simpler transistor base biasing arrangements are used to introduce self biasing. It has been found that the transistor can unintentionally be activated by environmentally generated interference signals.

The circuit design of this invention either biases the transistor to the near cut-of state or heavily in the on state. The supply voltages are well filtered by electrolytic capacitors and, because of the high dc. bias levels, a high noise and interference immunity factor results.

At no point is there any switching in the circuitry of FIGS. 17 and 19 to produce transients effecting transistor operation. The quiescent bias is fed through high value resistances to the bases of the driver transistors and since the unlighted photocell impedance is nearly infinite, the bias circuit produces the desired base bias conditions. Once the photocell is exposed to the lamp, the bias is rapidly overcome by the decreasing photocell resistance which provides the driver transistor base with an opposite polarity signal through the then lowimpedance photocell. This technique provides smooth switching conditions and provides an unusually noise immune circuit.

The circuiting of FIGS. 17 and I9 involves a swamping technique with reference to resistors 486 and 506,

and transistors 218 and 222, observing that impedance switching transistors have a very high collector-toemitter impedance when their base is at a low potential, but relatively low impedance when forward base biased. Referring to the example of the path of resistor 506 through transistor 222 to common line 479, once transistors 222 and 218 are biased positive, the voltage at points 514 and 496 is very low. This causes the output transistors 216 and 220 to assume a high emitterto-collector impedance which causes the relay to deenergize. The exact reverse occurs when negative bias is placed on the bases of the driver transistors.

The entire control circuit is strictly D.C. switching. No A.C. signals or voltage gains are involved which accounts for the extreme stability.

It will therefore be seen that we have provided a versatile precise pressure switching arrangement combined with an established pressure gauge arrangement that is available in either single or dual photocell actuated relay form. The reading of the gauge is uneffected by switch operation and the set points involved are readily adjusted with the external control knobs provided. Applied pressure and switch set points are fully visible at all times.

With this embodiment of the invention, deadband is one pointer width, less than I per cent of the full scale. Double throw relays can easily be interlocked to provide variable deadband control. The device is adapted for use with positive, negative, or differential pressures, and pressures as low as zero to 0.5 inches of water column, and as high as 0 to 20 psig full scale are available, as well as set points as low as 0.01 water column on a 0.5 inch scale unit.

The device can be used to control pressures in air conditioning systems, clean rooms, fluidic and pneumatic control systems, materials handling equipment, alarm or control fume exhaust systems and to monitor respiratory and blood pressures.

In the double circuit embodiment illustrated, the relay coils are deenergized when the gauge arm is to the left of the respective set point arms, and the relay coils are energized as the gauge arm passes to the right of the respective set point arms. Loss of electrical power has the same effect as loss of pressure, providing fail safe" protection.

The foregoing description and the drawings are given merely to explain and illustrate the invention and the invention is not to be limited thereto, except insofar as the appended claims are so limited, since those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

We claim:

1. In a combination pressure gauge and switch having a housing journaling a helix bearing an indicator arm movable therewith for cooperation with scale indicia facing outwardly of the housing, means for moving said helix in accordance with pressures sensed by the gauge, a pivotally mounted set point indicator arm cooperating with the scale indicia, a photocell movable with the set point arm and positioned to be exposed to a light source adjacent the helix for rendering same electrically conductive and to be shielded from same by a light shield movable with the helix at a predetermined position of the set point arm relative to the scale indicia whereby the cell isnon conductive, and electrical circuit means including said light source and said photocell for utilizing the position of the indicator arm relative to said set point arm to activate and deactivate an electrical relay coil, the improvement wherein:

said light source is aligned with the axis of said helix,

said light shield being movable about said helix axis and being shaped to be concentric therewith,

said circuit means including first and second switching semiconductors,

one of said semiconductors being in circuit controlling relation with said coil and the other of said transistors being in bias controlling relation to the first transistor,

and means connecting said second transistor to a dual polarity direct current power supply,

said photocell being electrically interposed in said connecting means to change the bias application to the second transistor in accordance with the exposure or shielding of the photocell with reference to the light source.

2. The improvement set forth in claim 1 wherein:

said relay coil comprises a component of a relay subassembly pack adapted to be secured to the housing or remotely located therefrom.

3. in a combination pressure gauge and switch device comprising an open ended housing having a helix journaled in same for rotation about its axis, with the helix having a pressure indicator arm movable therewith for cooperation with scale indicia facing outwardly of the housing open end, a magnet cooperating with the helix for producing pivoting movement of said helix in response to linear movement of said magnet longitudinally of the axis of the helix under the action of pressures sensed by the gauge, with the helix being journaled at the free end of a cantilevered supporting wishbone secured to the housing at the other end of same, a set'point indicator arm operably mounted on the wishbone for pivotal movement about the helix axis and cooperating with the scale indicia, a photocell movable with the set point indicator and positioned to be exposed to a light source adjacent the helix for rendering same electrically conductive and to be shielded from same by a light shield movable with the helix at a predetermined position of the set point arm relative to the scale indicia whereby the photocell is non conductive, electrical circuit means including said light source and said photocell for utilizing the position of the indicator arm relative to said set point arm to activate and deactivate an electrical device, means for adjustably positioning said free end of said wishbone to set the pressure indicator arm on the zero datum of the scale indicia, and a cover applied over the open end of the housing including a transparent portion for viewing said scale indicia and said arms, the improvement wherein:

said wishbone comprises a plate member of one piece construction defining between said ends thereof a planar portion at which the scale indicia are located,

said free end of said wishbone being indented outwardly of the housing relative to said planar portion to define a planar mounting panel portion in which one end of said helix is journaled,

said set point arm being secured to a gear segment journaled on the side of said wishbone panel portion facing outwardly of said housing for pivotal movement about the axis of said helix,

gear means journaled in said side of said wishbone panel portion for pivoting said gear segment to position said set point arm relative to said scale indicia,

said free end of said wishbone having a flange portion extending normally of said wishbone panel portion and terminating in a ledge that is in substantial parallelism with said wishbone in which the other end of said helix is journaled,

said wishbone flange portion being notched at one side of said helix and said light shield being on a support mounted on said helix and extending through said wishbone notch to dispose said light shield above said wishbone panel portion for movement about said helix axis,

said light source comprising a light bulb mounted above said wishbone mounting portion on said helix axis,

with said photocell being mounted on said gear segment on the outwardly facing side thereof.

4. The improvement set forth in claim 3 wherein:

said gear means is operated by a handle journaled in said cover and having a splined connection with said gear means for accommodating said adjustable positioning of said wishbone.

5. The improvement set forth in claim 3 wherein:

said gear means includes means for effecting pivotal movement of said set point arm in the same direction that said handle is turned.

6. The improvement set forth in claim 3 wherein:

said electrical circuit means includes a prong structure extending through said housing,

said prong structure comprising:

a multi-pronged plug mounted in a boss formed in said housing,

said boss projecting inwardly of the housing and said plug including a polygonal head disposed exteriorly of said housing,

with said plug extending short of the inwardly projecting portion of said boss with said prongs projecting through said boss portion into said housing for securement to wire means extending to said cell and said light,

said plug and said prongs being potted in place about said boss portion.

7. The improvement set forth in claim 6 including:

a locking clip cooperating between said plug head and said housing for fixing said plug against threading movement relative to said housing,

said clip comprising an annular member interposed between said plug head and said housing and having a tab in keyed relation to said housing and opposed flange portions seated against opposed faces of said plug head.

8. The improvement set forth in claim 3 wherein:

said housing has a flexible diaphragm mounted therein separating high and low pressure chambers,

with said low pressure chamber being on the back side of said housing,

said magnet being mounted on a leaf spring connected to said diaphragm to provide said linear movement of said magnet.

9. The improvement set forth in claim 3 wherein:

said housing includes a back wall having an exterior annular bearing surface,

said back wall having a cupped cap affixed thereto against said bearing surface,

with a diaphragm being clamped between said cap and housing back wall,

said housing back wall being formed with an opening aligned with said diaphragm,

said magnet being mounted on a leaf spring connected to said diaphragm to provide said linear movement of said magnet,

said cap being formed for connection to a source of fluid pressure.

10. The improvement set forth in claim 6 including a generally U-shaped bracket secured to the back wall of said housing,

said bracket having a web that is fixed to said housing back wall and a pair of legs extending normally of said back wall,

said legs having secured therebetween a panel board that extends parallelly of said housing back wall,

said panel board having said electrical device secured thereto on the side of same that faces said housing back wall,

with one of said legs being formed with a projecting end portion equipped with a pronged electrical connection plug adapted for plug in connection to electrical circuiting that is separate from said gauge,

wiring means extending between said housing multiprong plug and said side of said panel board for connecting said electrical device in said circuit means,

and wiring means extending between the other side of said panel board and said pronged connection for effecting connection of said circuit means to a source of electrical power.

11. The improvement set forth in claim 10 including:

a cover received over said bracket in abutting relation to said housing,

said cover being slotted in one side wall for frictional sliding engagement with said bracket one leg.

12. The improvement set forth in claim 3 wherein:

said electrical device comprises a relay coil,

and wherein said circuit means comprises:

a first switching transistor having its collector and emitter in series circuit with said coil,

a second switching transistor having the base of the first transistor connected to a series circuit which includes the second transistor collector and emitter,

and a controlling series circuit connected to a direct current dual polarity power supply and including the photocell in series circuit therewith and having the base of said second transistor connected thereto,

whereby when said photocell is shielded from said light source said first transistor is biased to energize said coil, and when said photocell is exposed to said light source, said first transistor is biased to de energize said coil.

13. The improvement set forth in claim 3 including:

a second set point arm operably mounted on the wishbone for pivotal movement about the helix axis and cooperating with the scale indicia,

said second set point arm being secured to a second gear segment journaled in said outwardly facing side of said wishbone panel portion,

gear means journaled in said side of said wishbone panel portion for pivoting said second gear segment independently of the first gear segment,

said second gear segment having a photocell mounted on same on the outwardly facing side thereof for exposure to said light source,

said light shield shielding the second photocell from the light source in at a predetermined position of the second set point arm relative to the scale indicia, whereby the second photocell is nonconductive,

said second photocell being incorporated in said electrical circuit means for utilizing the position of the indicator arm relative to the second set point arm to activate and deactivate a second electrical device. 

1. In a combination pressure gauge and switch having a housing journaling a helix bearing an indicator arm movable therewith for cooperation with scale indicia facing outwardly of the housing, means for moving said helix in accordance with pressures sensed by the gauge, a pivotally mounted set point indicator arm cooperating with the scale indicia, a photocell movable with the set point arm and positioned to be exposed to a light source adjacent the helix for rendering same electrically conductive and to be shielded from same by a light shield movable with the helix at a predetermined position of the set point arm relative to the scale indicia whereby the cell is non conductive, and electrical circuit means including said light source and said photocell for utilizing the position of the indicator arm relative to said set point arm to activate and deactivate an electrical relay coil, the improvement wherein: said light source is aligned with the axis of said helix, said light shield being movable about said helix axis and being shaped to be concentric therewith, said circuit means including first and second switching semiconductors, one of said semiconductors being in circuit controlling relation with said coil and the other of said transistors being in bias controlling relation to the first transistor, and means connecting said second transistor to a dual polarity direct current power supply, said photocell being electrically interposed in said connecting means to change the bias application to the second transistor in accordance with the exposure or shielding of the photocell with reference to the light source.
 2. The improvement set forth in claim 1 wherein: said relay coil comprises a component of a relay subassembly pack adapted to be secured to the housing or remotely located therefrom.
 3. In a combination pressure gauge and switch device comprising an open ended housing having a helix journaled in same for rotation about its axis, with the helix having a pressure indicator arm movable therewith for cooperation with scale indicia facing outwardly of the housing open end, a magnet cooperating with the helix for producing pivoting movement of said helix in response to linear movement of said magnet longitudinally of the axis of the helix under the action of pressures sensed by the gauge, with the helix being journaled at the free end of a cantilevered supporting wishbone secured to the housing at the other end of same, a set point indicator arm operably mounted on the wishbone for pivotal movement about the helix axIs and cooperating with the scale indicia, a photocell movable with the set point indicator and positioned to be exposed to a light source adjacent the helix for rendering same electrically conductive and to be shielded from same by a light shield movable with the helix at a predetermined position of the set point arm relative to the scale indicia whereby the photocell is non conductive, electrical circuit means including said light source and said photocell for utilizing the position of the indicator arm relative to said set point arm to activate and deactivate an electrical device, means for adjustably positioning said free end of said wishbone to set the pressure indicator arm on the zero datum of the scale indicia, and a cover applied over the open end of the housing including a transparent portion for viewing said scale indicia and said arms, the improvement wherein: said wishbone comprises a plate member of one piece construction defining between said ends thereof a planar portion at which the scale indicia are located, said free end of said wishbone being indented outwardly of the housing relative to said planar portion to define a planar mounting panel portion in which one end of said helix is journaled, said set point arm being secured to a gear segment journaled on the side of said wishbone panel portion facing outwardly of said housing for pivotal movement about the axis of said helix, gear means journaled in said side of said wishbone panel portion for pivoting said gear segment to position said set point arm relative to said scale indicia, said free end of said wishbone having a flange portion extending normally of said wishbone panel portion and terminating in a ledge that is in substantial parallelism with said wishbone in which the other end of said helix is journaled, said wishbone flange portion being notched at one side of said helix and said light shield being on a support mounted on said helix and extending through said wishbone notch to dispose said light shield above said wishbone panel portion for movement about said helix axis, said light source comprising a light bulb mounted above said wishbone mounting portion on said helix axis, with said photocell being mounted on said gear segment on the outwardly facing side thereof.
 4. The improvement set forth in claim 3 wherein: said gear means is operated by a handle journaled in said cover and having a splined connection with said gear means for accommodating said adjustable positioning of said wishbone.
 5. The improvement set forth in claim 3 wherein: said gear means includes means for effecting pivotal movement of said set point arm in the same direction that said handle is turned.
 6. The improvement set forth in claim 3 wherein: said electrical circuit means includes a prong structure extending through said housing, said prong structure comprising: a multi-pronged plug mounted in a boss formed in said housing, said boss projecting inwardly of the housing and said plug including a polygonal head disposed exteriorly of said housing, with said plug extending short of the inwardly projecting portion of said boss with said prongs projecting through said boss portion into said housing for securement to wire means extending to said cell and said light, said plug and said prongs being potted in place about said boss portion.
 7. The improvement set forth in claim 6 including: a locking clip cooperating between said plug head and said housing for fixing said plug against threading movement relative to said housing, said clip comprising an annular member interposed between said plug head and said housing and having a tab in keyed relation to said housing and opposed flange portions seated against opposed faces of said plug head.
 8. The improvement set forth in claim 3 wherein: said housing has a flexible diaphragm mounted therein separating high and low pressure chambers, with said low pressure chamber beinG on the back side of said housing, said magnet being mounted on a leaf spring connected to said diaphragm to provide said linear movement of said magnet.
 9. The improvement set forth in claim 3 wherein: said housing includes a back wall having an exterior annular bearing surface, said back wall having a cupped cap affixed thereto against said bearing surface, with a diaphragm being clamped between said cap and housing back wall, said housing back wall being formed with an opening aligned with said diaphragm, said magnet being mounted on a leaf spring connected to said diaphragm to provide said linear movement of said magnet, said cap being formed for connection to a source of fluid pressure.
 10. The improvement set forth in claim 6 including a generally U-shaped bracket secured to the back wall of said housing, said bracket having a web that is fixed to said housing back wall and a pair of legs extending normally of said back wall, said legs having secured therebetween a panel board that extends parallelly of said housing back wall, said panel board having said electrical device secured thereto on the side of same that faces said housing back wall, with one of said legs being formed with a projecting end portion equipped with a pronged electrical connection plug adapted for plug in connection to electrical circuiting that is separate from said gauge, wiring means extending between said housing multiprong plug and said side of said panel board for connecting said electrical device in said circuit means, and wiring means extending between the other side of said panel board and said pronged connection for effecting connection of said circuit means to a source of electrical power.
 11. The improvement set forth in claim 10 including: a cover received over said bracket in abutting relation to said housing, said cover being slotted in one side wall for frictional sliding engagement with said bracket one leg.
 12. The improvement set forth in claim 3 wherein: said electrical device comprises a relay coil, and wherein said circuit means comprises: a first switching transistor having its collector and emitter in series circuit with said coil, a second switching transistor having the base of the first transistor connected to a series circuit which includes the second transistor collector and emitter, and a controlling series circuit connected to a direct current dual polarity power supply and including the photocell in series circuit therewith and having the base of said second transistor connected thereto, whereby when said photocell is shielded from said light source said first transistor is biased to energize said coil, and when said photocell is exposed to said light source, said first transistor is biased to de-energize said coil.
 13. The improvement set forth in claim 3 including: a second set point arm operably mounted on the wishbone for pivotal movement about the helix axis and cooperating with the scale indicia, said second set point arm being secured to a second gear segment journaled in said outwardly facing side of said wishbone panel portion, gear means journaled in said side of said wishbone panel portion for pivoting said second gear segment independently of the first gear segment, said second gear segment having a photocell mounted on same on the outwardly facing side thereof for exposure to said light source, said light shield shielding the second photocell from the light source in at a predetermined position of the second set point arm relative to the scale indicia, whereby the second photocell is nonconductive, said second photocell being incorporated in said electrical circuit means for utilizing the position of the indicator arm relative to the second set point arm to activate and deactivate a second electrical device. 